1.Defrag your computer regularly. This will allow your hard drive to not work as hard which won't drain your NOKIA BC-3S battery more.
2.Lower the brightnest of your screen. The brighter your screen, the more power being used.
3.Try to keep the amount of programs to a minimum. Every program open helps drain the battery a little bit more.
4. Cut down on external devices, such as USB devices, like a mouse. Also WiFi will drain your NOKIA BC-3S battery so turn it off when you aren't using it to save power.
5.Clean the NOKIA BC-3S Battery contacts. Every 6 months are so you should take out your battery and clean the contacts that connect to the laptop. You can use a cloth with rubbing alcohol to achieve this.
6.If you ever put your computer on standy, you should try to switch to hibernate, as hibernate fully shuts down your computer, but it allows you to quickly resume your work when you turn it back on.
7.Go to "Power Options" on your laptop and change it's setting to Max Battery, Super Energy Saver, or one of the other many different forms of it. But it all means the same thing, switch to the setting that is set for saving the most amount of energy.